Utility steam is typically available at superheated conditions for heat transfer applications. Superheated steam is less efficient for heat transfer than saturated steam. Superheated steam requires more exchanger surface area than an appropriate level of saturated steam to achieve the same energy input.
A refinery typically operates several levels of utility steam headers. The high pressure steam level is nominally 600 psig and is superheated to ˜700° F. These conditions are too severe for direct application as reboiler heat source for several distillation tower applications in the refinery. For instance, the steam is too hot for use in debutanizer reboiler service. The high temperature steam can be cooled by injecting water. However, traditional desuperheaters are complex, expensive, and suffer from poor reliability.
Traditionally, utility steam is de-superheated by the controlled injection of condensate to reduce superheat prior to use in heat exchangers. These injection type desuperheaters require a high pressure condensate source (typically requiring a new pump), an in-line injection nozzle and control valve, and are prone to reliability problems in field service.